2005 Annual Report for GNC03-017
Effect of Sustainable Ground Floor Management Systems on Root System Dynamics of Apple and their Contribution to Carbon Sequestration and Nutrient Cycling in the Soil
Summary
The evaluation of three ground floor management systems for organic apple orchards suggests that the Swiss Sandwich System (SSS) is promising for Michigan and other states with similar climate. Mulching (alfalfa hay) increases significantly the amount of available nitrogen and organic matter in the soil compared with the other two systems. Flaming and SSS release the same. Mulching actually releases too much nitrogen risking leaching problems.
Root dynamics were affected from the treatments under evaluation behaving differently depending on time of the year, position related to the tree, and depth in the soil profile.
The systems affect the soil food web with mulching and SSS creating a comparable environment while flame has the lowest population numbers.
Objectives/Performance Targets
Investigate the behavior of apple trees fine roots (timing and rate of growth, and their turnover) subjected to two different ground managements under the organic protocol.
Amount of carbon sequestered in the soil by the trees.
Effects of fine root turnover on nutrient cycling, food-web and soil sustainability.
Introduction of the best ground floor management system for the desired growing conditions.
Accomplishments/Milestones
In 2005 we have finally received the availability to use the new developed software for the measurement of roots from the pictures obtained by minirhizotrons.
During 2005 the pictures collected from the year 2003 have been analyzed. The pictures from year 2004 are still under analysis.
Regarding the above ground part of the trees, the amount of pruning wood, trunk calipers, shoot growth, and yield coming from the 2004 season have been measured and analyzed. Some measurements have been taken in the 2005 season except for the pruning wood and the trunk calipers that will be measured after the winter.
84 samples of soil have been taken four times a year during 2005 (for a total of 336 each year) and analyzed for available nitrogen (NO3-and NH4+), organic matter and carbon content. 2005 data are still under processing and evaluation.
48 soil samples (collected in April 2005) from the treatments have been tested for soil food web composition through soil nematode counting.
Regarding the 2005 season we noticed a difference between the systems related to the amount of carbon and nitrogen returned to the soil with mulch being the highest and flaming being the lowest. The Sandwich system performed in the middle.
The three systems have an effect on nitrate availability in the soil with mulch (alfalfa hay) showing the highest value and Flaming the lowest. However the nitrogen content in the soil for the SSS and Flaming has permitted healthy growth.
The treatments do not have a significant effect on plant growth in 2005, however the rootstocks did, and no interaction between treatments and rootstocks was found. Supporter 4 was the most vigorous followed by M9. RN 29, and M9. NAKB 337.
Regarding the effect of the treatments on Organic Matter (OM) till 2005, no differences between systems were found at the depths of 0-30 cm. At 0-10 cm depth we noticed that mulch has the highest amount of OM while Flame has the lowest. Since the beginning of the experiment we measured an increase in OM in the treatment mulch, no differences in the Sandwich system, and a slight decrease in the Flame.
In the 2005 harvest there was significant interaction between treatment and rootstock with M9. RN 29 producing the highest yield in the sandwich treatment and in the flaming one. The other two rootstocks performed the same independently from the treatment. M9. RN 29 seems the most adapted rootstock for the treatments Flame and Sandwich system, where the soil conditions were less optimal than in the Mulch treatment (regarding N and OM).
Regarding the soil food web composition the three systems had an impact on soil food web with mulch and SSS creating the same environment while flaming had the lowest population numbers. During the period under analysis we noticed an increase of bacteria feeding nematodes in the Mulch treatment, while there was an increase in fungal feeding nematodes in the Sandwich system one. The Flame treatment fluctuated during the season and during the years. The Sandwich System treatment seems to have the most balanced food web between the treatments.
In 2005 minirhizotrons have been extracted from the soil because a long permanence (over 2 years) affects the root growth.
Regarding the root growth dynamics the data obtained from the pictures from the year 2003 have been evaluated considering the root area, since it is comprehensive of length and diameter.
Only two (Mulch and Sandwich system) of the three treatments under evaluation have been monitored for root dynamics with minirhizotrons, since the plastic tubes would have reacted poorly to flaming.
The 2 treatments did have an impact on Root dynamics with Sandwich having a higher area at the beginning of the season and Mulch at the end. Sandwich showed a higher area underneath the tree canopy at almost every depth especially early in the season. Mulch showed a growth at 0-30 cm underneath the tree canopy late in the season. Treatments showed different root dynamics below 90 cm depth at 53 cm from the trunk for sandwich and at 68 cm for mulch.
In addition all the data will be analyzed for significance, yearly and in time to asses the long term effect.
Impacts and Contributions/Outcomes
In 2005, 68 growers attended the field day. Five talks were given on the project at local, national and international conferences.
In 2005 a grower volunteered 5 acres to try the Swiss Sandwich System (one of the systems under evaluation in the project) to try it at a commercial scale.